I believe it's density but I'm not sure. What make cheesecake a NY style? Is there different ingredients. Some people call their recipe NY Cheesecake and they are not.
New York-style cheesecake, made famous by Lindy's and Junior's Deli, relies upon heavy cream, cream cheese, eggs and egg yolks to add a richness and a smooth consistency. Also called Jewish-style, it is baked in a special 5- to 6-inch tall springform pan in many restaurants. Some recipes use cottage cheese and lemon for distinct texture and flavor or add chocolate or strawberry to the basic recipe.
New York style cheesecakes are cream cheese mixtures baked without a water bath and are unique because the baking starts at a high temperature (that's quickly dropped down) producing a rich interior and light brown exterior. A NY cheesecake is high, dense, and firm.
or refer this link : http://www.crumblycookie.net/2010/09/12/cheesecake-comparison/